The object of this study is the assessment of patterns of infection with microbial pathogens linked to periodontal disease in families participating in the Multigenerational Study of Periodontitis in the Piedmont area of North Carolina. The study sample includes members of nuclear families ascertained through individuals studied as part of a population-based epidemiologic study of elder North Carolinians, regardless of periodontal status. Clinical, behavioral, and immunological measures were obtained for study. In a subset of these persons, who were found to have severe periodontal disease, extended family structures were sampled. Analyses to date provide evidence of significant levels of familial aggregation of infection status, with stronger levels of maternal than paternal association. Analyses incorporating adjustment for relevant covariates are in progress.[unreadable]